The present invention is directed to electrically-powered evacuation devices for use in evacuating a prosthetic socket and/or to prosthetic limbs incorporating such electrically-powered evacuation devices. The present invention is also directed to various systems and methods for monitoring, performing, and controlling such devices.
Artificial limbs have been in use throughout history, having been first recorded circa 2750 B.C. During that period of time, interfacing and suspending an artificial limb has been a continuing challenge. Various and numerous theories and anatomical constructs have been used over time in an evolving manner, and these have revealed a number of key factors in maximizing comfort and functional potential for persons who wear artificial limbs.
Firstly, the surgical procedure used to perform limb amputation is an important factor. The size and shaping of the patient's residual limb is often important to the comfort the patient will later have with a prosthesis. Stated simply, it is critical that the residual limb and prosthesis interface tightly and couple and distribute pressure evenly across the surface of the residual limb.
Early versions of artificial limbs required the use of leather or equivalent straps or belts to suspend the artificial limb upon the person. Later systems employed linkage techniques such as condylar wedges, rubber or synthetic elastic tubing, thermoplastic roll-on sleeves with pin locking systems, and sub-atmospheric pressure. Of these, sub atmospheric pressure is typically often preferred, because it creates a linkage that provides maximum proprioceptive feedback and control for the artificial limb user. It also provides the best linkage between the user's limb and the prosthetic device.
Creating a reliable sub atmospheric pressure chamber between the residual limb and prosthetic device has, however, proved to be a challenge. As new airtight thermoplastic and thermo set materials have evolved, along with airtight thermoplastic roll-on liners, the potential for creating a sub-atmospheric pressure within the prosthetic chamber (socket) has improved. Specifically, the patient's residual limb is covered with a roll-on urethane or other thermoplastic liner, which helps to protect the user's tissue from unwanted isolated high negative pressure values, and provides cushioning for the tissue at the same time. The liner also helps to distribute the sub-atmospheric pressure applied to the user's limb in a more uniform manner.
Several mechanical means for creating an elevated negative pressure chamber within a prosthetic socket have emerged. One method disclosed in U.S. Pat. No. 6,554,868, utilizes a weight activated pump, in which sub atmospheric pressure is maintained strategically within the socket as the user walks. Under this approach, vacuum is maintained as the patient ambulates with the artificial limb.
This method of evacuating a prosthetic socket has several disadvantages, however. First, the weight activated pump is heavy, and cannot be removed even in the case of a pump failure. The weight activated pump also requires a certain minimum space between the user's limb and prosthetic foot, which may be more than is available if the patient has a relatively long residual limb. This prohibits the use of this technology for many artificial limb users. Further, a weight-activated pump system requires some number of weight activated strokes before becoming effective.
Another evacuation method disclosed in the above-referenced patent uses a hand-held sub-atmospheric pressure pump, much like that used to bleed brake systems on an automobile. This method provides for acceptable socket evacuation, but requires the individual to carry the hand-held pump upon their person for use in case of vacuum failure. The hand-held pump is also awkward for many individuals to use and requires a certain amount of dexterity and strength to operate. This is a common problem for elderly individuals.
As can be understood from the foregoing discussion, known mechanical systems for evacuating a prosthetic socket have several disadvantages. Aside from those specific disadvantages detailed above, such mechanical systems are further burdened with other general problems. Primarily, the evacuation pump associated with such systems is active only when the user is ambulating, and then is activated with every step—regardless of the wishes of the user.
Therefore, one general disadvantage to such a mechanical systems is that the pump is unable to draw vacuum when the user is sedentary. This means that absent the carrying and use of a separate hand-held pump, there is no way to properly don an associated prosthesis without standing up and walking on the prosthesis in a partially donned (i.e., non-evacuated) state. Similarly, if the socket loses pressure while the user is sitting or otherwise non-ambulatory, there is no way (aside from a separate hand-held pump) to re-evacuate the socket other than walking or bouncing on the now improperly suspended prosthesis.
Yet another disadvantage to such mechanical evacuation systems is that a weight-activated pump will always eventually evacuate the prosthetic socket to some predetermined level. As such, there is no way for a user to adjust the level of vacuum to coincide with a particular activity or comfort level. For example, a user would not be able to increase the vacuum level over some typical vacuum level during a period of increased activity, nor decrease the vacuum level to compensate for a particularly sore or sensitive residual limb.
Thus, there is a need for improved means of achieving sub-atmospheric pressure within a prosthetic socket. The present invention satisfies this need.